Should this be EINVAL, or EOPNOTSUPP? Usually EINVAL means there is
something wrong with the passed ioctl parameters (e.g. bad value),
while EOPNOTSUPP is "operation not supported" and makes more sense.

Sounds good.
I will send new patch-set which is rebased to 2.6.26-rc3 and includes
this fix, in this weekend.
Cheers, Takashi